The Italian War of 1551 (1551–1559), sometimes known as the Habsburg–Valois War and the Last Italian War, began when Henry II of France, who had succeeded Francis I to the throne, declared war against Charles I of Spain with the intent of recapturing Italy and ensuring French, rather than Habsburg, domination of European affairs.

The 1551 Ottoman Siege of Tripoli was the first step of the all-out Italian War of 1551–59 in the European theater, and in the Mediterranean the French galleys of Marseilles were ordered to join the Ottoman fleet.[3] In 1552, when Henry II attacked Charles V, the Ottomans sent 100 galleys to the Western Mediterranean,[4] which were accompanied by three French galleys under Gabriel de Luetz d'Aramon in their raids along the coast of Calabria in Southern Italy, capturing the city of Reggio.[5] In the Battle of Ponza in front of the island of Ponza, the fleet met with 40 galleys of Andrea Doria, and managed to vanquish the Genoese and capture 7 galleys. This alliance would also lead to the combined Invasion of Corsica in 1553. The Ottomans continued harassing the Habsburg with various operations in the Mediterranean, such as the Ottoman invasion of the Balearic islands in 1558, following a request by Henry II.[6]

The Treaty of Vaucelles was signed on 5 February 1556 between Philip II of Spain and Henry II of France. Based on the terms of the treaty, the territory of the Franche-Comté was relinquished to Philip. However, the treaty was broken shortly afterwards.

After Charles' abdication in 1556 split the Habsburg empire between Philip II of Spain and Ferdinand I, the focus of the war shifted to Flanders, where Philip, in conjunction with Emmanuel Philibert of Savoy, defeated the French at St. Quentin. England's entry into the war later that year led to the French capture of Calais, and French armies plundered Spanish possessions in the Low Countries. Nonetheless, Henry was forced to accept a peace agreement in which he renounced any further claims to Italy.

The wars ended for other reasons, including the Double Default of 1557, when the Spanish Crown, followed quickly by the French, defaulted on their debts. In addition, both sides had to confront Protestantism at home, which they both hoped to crush.[7]

The French had achieved mixed results : their situation had improved significantly when compared to the late 1520s, they had made some territorial gains and the treaty was considered an agreement between two equal powers. However, they had failed to change the balance of power in Italy, or breaking the Habsburg encirclement. Most importantly, their good position would soonly be jeopardized by the French Wars of Religion. For the Habsburgs as a whole, the result was mixed too, as the war had weakened their position in the Holy Roman Empire and led to the separation of Charles' realm. However, for the Kingdom of Spain, the results were much better, as it was left as the sole dominant power in Italy and had successfully withstood the French effort. England fared poorly during the war, and the loss of its last stronghold on the continent damaged its reputation.